Fix typos in README and bugs in RAG example code for end-to-end evaluation and finetuning (#9355)

* fix a bug in eval_batch_retrieval

* should return parser as well as other staticmethod

* remove duplicate argument

* these kwargs are no longer accepted (cause TypeError in self.generator.generate of modeling_rag.py)

* fixed file paths in README

* moved an arg to add_ray_specific_args

examples/research_projects/rag/eval_rag.py

@@ -130,8 +130,6 @@ def evaluate_batch_e2e(args, rag_model, questions):
             early_stopping=False,
             num_return_sequences=1,
             bad_words_ids=[[0, 0]],  # BART likes to repeat BOS tokens, dont allow it to generate more than one
-            clean_up_tokenization=True,
-            print_docs=args.print_docs,
         )
         answers = rag_model.retriever.generator_tokenizer.batch_decode(outputs, skip_special_tokens=True)